This invention relates to a compass and, more particularly, to an electronic compass assembly and methods for controlling an electronic compass assembly.
Electronic compass assemblies are often used in vehicles to indicate to a driver or passenger of the vehicle a direction that the vehicle is facing or traveling. A typical electronic compass assembly includes magnetic sensors that detect a magnetic field of the Earth. A microprocessor typically then determines the direction of the vehicle from the detected magnetic field and displays the direction as one of North, South, East, West, Northeast, Northwest, Southeast, and Southwest.
The magnetic conditions of the vehicle and surrounding environment of the vehicle typically change over time. As a result, the magnetic sensors are periodically calibrated to correct the magnetic field data for these magnetic changes. Calibration typically includes collecting magnetic field data from the magnetic sensors through a 360° turn of the vehicle (or a predetermined percentage of a 360° turn). The collected magnetic field data is generally ellipse-shaped. The microprocessor utilizes a statistical fitting procedure to produce a reference correction factor (e.g., a calibration ellipse) from the collected magnetic field data. The reference correction factor is then used to correct magnetic field data points before the microprocessor determines the vehicle direction.
Typical electronic compass microprocessors receive raw magnetic field data from the magnetic sensors. The microprocessor typically filters the raw magnetic field data before calibration to improve the reliability and accuracy of the calibration by removing or smoothing noisy data points. The filtered magnetic field data is then used in the calibration computation. The filtered data is subsequently used in the compass heading computation. Although the filtering is intended to improve the reliability and accuracy of the calibration computations, it may hinder the reliability and accuracy of the compass heading computation because what is determined to be noisy data for the calibration computation is not necessarily noisy data for the compass heading computation, for example. Likewise, tuning the filtering to improve the reliability and accuracy of the compass heading computation may hinder the reliability and accuracy of the calibration computation.
Accordingly, there is a need for an electronic compass assembly and method that provides for independent control over the calibration computation and the compass heading computation. This invention addresses those needs and provides enhanced capabilities while avoiding the shortcomings and drawbacks of the prior art.